In known projectors a convergence device is used of the type comprising a plate on which a concerned light modulator is fixed, whereby this plate is slidably mounted on the frame of the projector and secured in place by means of a plurality of fixation screws.
An intervention to readjust the convergence requires loosening of these screws, slidably adjusting the position of the plate and tightening the screws again according to a predetermined sequence.
A disadvantage of this kind of convergence device is that tightening of these screws affects the alignment of the plate, therefore requiring up to eight iterations to fix the plate in the desired position. This requires patience and diligence of an experienced person with steady hands.
A complete operation for readjusting the convergence of such known projectors typically lasts thirty minutes and more.
Another disadvantage of present systems is that the light modulators are typically mounted with their edges forming an angle with the vertical. In order to shift the projected image in a vertical direction on the projection screen, the concerned light modulator has to be moved in an angled direction, making corrections even more difficult.
Another disadvantage is that access to the adjustment screws is often very difficult. This is further complicated by building projectors with an hermetically sealed housing. In such cases a correct intervention would require shipment to the lab to open the sealing in a controlled dustfree environment.